1. Field of the Invention
The present invention relates generally to a disc case in which a recording disc such as CDROM or the like is releaseably received. More particularly, the present invention relates to a disc case including a shutter opening/closing mechanism which is actuated with the aid of a spring member.
2. Description of the Prior Art
One of conventional disc cases is shown in FIG. 7. The disc case in which a disc is releaseably received includes a housing 1 and a cover (not shown). In addition, a shutter 2 is slidably disposed on the opposite side to a cover fitting surface of the housing 1 (hereinafter referred to as a rear surface) so as to properly expose a part of the disc to the outside for the purpose of recording or reproducing.
The housing 1 has a disc receiving portion 3 formed in a central region thereof, and the shutter 2 slidably disposed on the rear surface of the housing 1 is normally fully closed with the aid of a spring member 4. When a recording or reproducing operation is performed with the disc in a certain apparatus or equipment (not shown), the shutter 2 is translationally displaced against a resilient force of the spring member 4 in the leftward direction as seen in the drawing.
The aforementioned disc case is disclosed in an official gazette of Japanese Laid-Open Utility Model NO. 63-91870. According to this prior invention, the spring member 4 is designed in a widely opened V-shaped contour as seen in a plan view and a single turn portion is formed at the intermediate part of the spring member 4.
With the conventional disc case as constructed in the above-described manner, however, it has been found that the disc case has problems that the spring member 4 is easily broken because merely a single turn portion is formed on the spring member 4 and, if the number of turns of the turn portion increases, the turn portion becomes thick and thereby opposite ends of the turn portion come in contact with the inner wall surface of the housing 1. Another problem is that the spring 4 tends to collide against a boundary wall 5 defining a part of the disc receiving portion 3 because merely a single bent portion (i.e., turn portion) is formed on the spring member 4, resulting in return movement of the spring member 4 failing to be carried out correctly and smoothly.
To obviate the foregoing problems, the inventor has made a proposal as disclosed in an official gazette of Japanese Laid-Open Utility Model NO. 63-130975. According to this prior invention, a disc case in which a disc is releaseably received includes a housing 6 having a disc receiving portion formed in a central region thereof, a shutter 7 adapted to slidably move along one brim of the housing 6 to properly expose a part of the disc to the outside and a spring member 9 for generating a resilient force active in the direction of closing the shutter 7, one end of the spring member 9 being engaged with a groove 8 formed in one corner section of the housing 8, while other end of the spring member 9 being engaged with one side end of the shutter 7 opposite to the corner section of the housing 8, wherein the spring member 9 includes at least two turn portions 10, as shown in FIG. 8.
With the spring member 9 including two turn portions as shown in FIG. 8, no problem occurs, when the housing 6 has a wide spring receiving portion in which the spring member 9 is received. However, when the spring receiving portion is dimentioned small such that the spring member 9 is received in a narrow space, there arise problems that as the shutter 7 is repeatedly opened and closed many times, a property of slidable movement of the shutter 7 is increasingly degraded due to frequent frictional contact of the spring member 9 with a boundary wall defining a part of the disc receiving portion and moreover a number of fine waste particles in the form of resin grains is produced from the boundary wall defining a part of the disc receiving portion because of the aforementioned frequent frictional contact. Particularly, in a case where the spring receiving portion is jointed to the disc receiving portion, the disc is unavoidably contaminated with such fine waste particles. For the reason, any oil is not allowed to be used for the spring member 9. Thus, it has been heretofore required to satisfactorily solve the problem on undesirable frequent frictional contact. In view of the foregoing problems, a proposal has been made such that an angle .zeta. of the spring member 9 in FIG. 8 is increased. This proposal is effective for preventing the aforementioned frictional contact from occurring frequently and minimizing a quantity of fine waste material derived from the repeated frictional contact. However, the problem on durability of the spring member 9 is left still unsolved, because a force exerted on the spring member 9 when the shutter 7 is fully closed becomes excessively large.